Adjustable cerebrospinal fluid shunt valves in 3.0-Tesla MRI: a phantom study using explanted devices

Considering the rapidly increasing number of clinical high-field MR imagers and the lack of data regarding interference with magnetically adjustable cerebrospinal fluid (CSF) shunt valves, valve safety was assessed with regard to magnetic field interactions: imaging artifacts, heating, magnetic forces, and functional changes in a phantom study at 3.0 Tesla using explanted devices as a realistic model for in vivo conditions.

Sixteen explanted Codman-Medos and Sophy-SU8 shunt valves, all in perfect working order, were selected and exposed to a 3.0 T static magnetic field. Valve-induced imaging artifacts and signal drop-outs and the heating experiments were evaluated using standard diagnostic MR sequences with different SAR values. Translational attraction for the adjustable valves was assessed using the deflection angle method. To test adjustability and function, the spherical phantom containing the valve was placed in the isocenter of the MR scanner and exposed to a static magnetic field of 3.0 T for 0.25 to 12 hours (repeated exposure 1-12 times), including typical entrance and move-out procedures.

The diameters of imaging artifacts ranged from 10-70 mm and were most prominent on T2*w sequences. There was no relevant MR-imaging-related heating. Magnetic forces were not critical. Reproducible adjustment failures occurred in 6 valves.

Until suggestions can be made concerning the exposure of hydrocephalic patients to 3.0 T-MRI, further testing is necessary.